A number of isoindole-type compounds are known in the prior art.
Recently, in German Offenlegungsschrift No. 2,165,651 a group of isoindole-1,3-diones which are useful as herbicides was disclosed. The general formula for the isoindole-1,3-diones disclosed in the Offenlegungsschrift is as follows: ##STR1## wherein R may be an aryl, aralkyl or benzyl optionally substituted with 1 to 5 halogen atoms; hydroxy, nitro, cyano, thiocyano, carboxy, halogenated alkyl, or alkyl, or alkoxy, lower alkylthio, phenyl groupings and a group having the configuration --O--CH.sub.2 A may also be substituted therein, wherein A is a phenyl or a naphthyl group, wherein the phenyl group may have one or more substitutions therein, such as halogen atoms, nitro groupings, lower alkyl groupings or lower alkoxy groupings.
Typical of the compounds disclosed in the Offenlegungsschrift is the compound of Example 1: ##STR2##
Although the compounds disclosed within the Offenlegungsschrift are active herbicides, the need still exists for herbicides which are more active still. The presence of undesired vegetation is very damaging to useful crops such as rice. In the current world situation, wherein food shortages are acute, it is more important not to lose a portion of a valuable crop such as rice. The presence of such undesired vegetation results in the loss of a significant portion of such crops. Thus, a need exists for a particularly effective herbicide which will destroy as much of this unwanted vegetation as is possible without causing significant damage to the desired crops, e.g. rice.
According to the instant invention, herbicidal compounds have been discovered which are highly active herbicides and yet cause minimal damage to certain desired crops, e.g. rice.
In U.S. Pat. No. 2,900,243, there is a disclosure of herbicidal activity for 2-(4-halophenyl)-3a,4,5,6,7,7a-hexahydro-1H-isoindole-1,3(2H)-diones; the phenyl and 2-chlorophenyl analogs are described as being inactive as herbicides.